fixup: sign_message doc now clarifies about the prefix before signing

Author: martinsaposnic

lightning/src/sign/mod.rs

@@ -933,7 +933,8 @@ pub trait NodeSigner {
 
 	/// Sign an arbitrary message with the node's secret key.
 	///
-	/// Creates a digital signature of a message given the node's secret.
+	/// Creates a digital signature of a message given the node's secret. The message is prefixed
+	/// with "Lightning Signed Message:" before signing.
 	/// A receiver knowing the node's id and the message can be sure that the signature was generated by the caller.
 	/// An `Err` can be returned to signal that the signer is unavailable / cannot produce a valid
 	/// signature.